1. Field of the Disclosure
The disclosure relates to data link communications from aircraft.
2. Introduction
An Automatic Dependent Surveillance-Broadcast (ADS-B) equipped aircraft determines its own position using a global navigation satellite system and periodically broadcasts this position and other relevant information to potential ground stations and other aircraft with ADS-B-in equipment. ADS-B can be used over several different data link technologies, including Mode-S Extended Squitter (1090 ES), VHF data link (vDL Mode 4), and Universal Access Transceivers (UAT).
ADS-B provides accurate information and frequent updates to airspace users and controllers, and hence supports improved use of airspace, reduced ceiling/visibility restrictions, improved surface surveillance, and enhanced safety, for example through conflict management.
Under ADS-B, an aircraft periodically broadcasts its own state vector and other information without knowing what other vehicles or entities might be receiving it, and without expectation of an acknowledgment or reply. ADS-B is automatic in the sense that no pilot or controller action is required for the information to be issued. It is dependent surveillance in the sense that the surveillance-type information so obtained depends on the suitable navigation and broadcast capability in the source aircraft.
There is a growing international consensus that ADS-B will become the cornerstone technology of the next-generation air traffic management (ATM) systems. This is primarily due to the substantial cost benefits and technical advantages over current radar systems. The lower cost differential of building and maintaining current radar systems and the other tangible benefits accrued directly to Air Traffic Control (ATC) providers is driving significant investment in ADS-B implementation activity in the global aviation arena.
ADS-B is viewed by the FAA, NavCanada, AirServices Australia, Eurocontrol and other global ATM organizations as the single unifying ATM system of the future. While initial trials of ADS-B deployment occurred in areas with limited primary radar coverage, it is envisioned that within 10-15 years, ADS-B will supplement, if not totally replace primary radar functionality. Moreover, it is highly likely that secondary radar will be maintained as a backup capability. It is critically imperative that the standards being developed are harmonized in concert amongst all ATM organizations worldwide.
Other implications in attempting to further the implementation of any national ADS-B capability are that CAA/ATM organizations need to negotiate standards within their internal constituencies (ATC users), as well as with external constituencies (Airlines and Airports) somewhat simultaneously. Other users, particularly airlines, need to be part of the equation as they are required to be equipped in order to achieve the overall benefit.
One of the major obstacles to implementing a national ADS-B system has been the reluctance of some airlines to equip older aircraft with ADS-B avionics as these airlines do not see a great benefit or return on their investment. A case in point is the NavCanada implementation in the Hudson Bay non-radar airspace that underwent a process of obtaining airline buy-in and developed a business case for ADS-B/Out Only as compared to radar. The outcome of the business case analysis was an estimated $200M in fuel savings alone due to reduced separation minimums and other routing advantages. Operational benefits generated by controller operations (reduced communication work load, less time providing IFR separation etc.) were not reported to be part of the benefit calculation.
It is universally felt that the primary benefits of ADS-B are focused on ATC for separation, but there are many other benefits that can be obtained by both ATC providers and other airspace users—namely airlines and airports. This is clearly evident by observing the growing demand for products and services that assist airline and airport customers in flight following and tracking. Many products rely on real-time aircraft positional information that is not currently available in the continental USA. Additionally, ADS-B can also provide a capability to augment airport surface tracking in some environments to automatically generate block time and OOOI messages in a non-ACARS capable/equipped areas. These messages have been proven to lower airline operating costs and improve efficiency and are highly desired by the customer base.